Add static property for default RedisConnection port

Motivation:

The default port for Redis is well published to be 6379, and it is common to want to pass this value around or use it as a static default value in methods and initializers.

Modifications:

Add `RedisConnection.defaultPort` static property for all users to use, and update references of the `6379` literals to use new  the new property.

Result:

Users should have a reliable default defined to use everywhere to avoid bugs.

README.md

@@ -38,7 +38,7 @@ and run the following command: `swift package resolve`
 import RedisNIO
 
 let connection = Redis.makeConnection(
-    to: try .init(ipAddress: "127.0.0.1", port: 6379),
+    to: try .init(ipAddress: "127.0.0.1", port: RedisConnection.defaultPort),
     password: "my_pass"
 ).wait()
 

Sources/RedisNIO/Redis.swift

@@ -64,7 +64,7 @@ extension Redis {
     ///
     ///     let elg = MultiThreadedEventLoopGroup(numberOfThreads: 3)
     ///     let connection = Redis.makeConnection(
-    ///         to: .init(ipAddress: "127.0.0.1", port: 6379),
+    ///         to: .init(ipAddress: "127.0.0.1", port: RedisConnection.defaultPort),
     ///         using: elg,
     ///         password: "my_pass"
     ///     )

Sources/RedisNIO/RedisClient.swift

@@ -56,6 +56,8 @@ private let loggingKeyID = "RedisConnection"
 ///
 /// See `RedisClient`
 public final class RedisConnection: RedisClient {
+    public static let defaultPort = 6379
+
     private enum ConnectionState {
         case open
         case closed

Tests/RedisNIOTests/Utilities/RedisConnection.swift

@@ -19,7 +19,10 @@ extension Redis {
     static func makeConnection() throws -> EventLoopFuture<RedisConnection> {
         let env = ProcessInfo.processInfo.environment
         return Redis.makeConnection(
-            to: try .makeAddressResolvingHost(env["REDIS_URL"] ?? "127.0.0.1", port: 6379),
+            to: try .makeAddressResolvingHost(
+                env["REDIS_URL"] ?? "127.0.0.1",
+                port: RedisConnection.defaultPort
+            ),
             password: env["REDIS_PW"]
         )
     }